1. Field of the Invention
The present invention relates to a one-part polyurethane resin composition with improved mechanical and chemical properties, a method of preparing the same, and a method of preparing a paint composition having the same. More particularly, the present invention relates to a one-part polyurethane resin composition, which reduces drying time and recoating time and improves chemical resistance of a coated film, a method of preparing the same, and a method of preparing a paint composition having the same.
2. Description of the Related Art
Resins for coating woods are of various kinds. A typical example of one-part paint is lacquer paint for wood filling containing nitrocellulose. The lacquer paint dries fast, but a coated film using the lacquer paint has poor chemical resistance and hardness. Another example of the one-part paint is ultra-violet curable paint. The ultra-violet curable paint, however, requires an expensive ultra-violet curing apparatus.
Two-part paints having polyols and a urethane curing agent, or two-part paints that are acid curable are variously used to coat wood products. Pot life needs to be considered in the two-part paints, because a main agent and a curing agent are mixed. Moreover, recoating a film takes a long time, and a curing process requires particular conditions such as room temperature drying or heating drying depending on characteristics of polyols and a urethane-curing agent. Thus, the two-part paints require a lot of processing time and additional expenses.
Therefore, a one-part polyurethane resin composition, which has a short film drying time, a short recoating time and an improved mechanical properties such as film hardness and chemical resistance and has alleviated processing conditions, is required for wood filling, under coating or top coating.
In addition, methods of preparing the one-part polyurethane resin composition and a paint composition having the same are required, in which a copolymerization reaction of a hard segment and a soft segment is uniformly conducted and a coated film has no partial gloss deterioration caused by a curing rate difference and no wrinkling when recoated.